Medical instruments of this type can be, for example, a grasping, holding or dissecting forceps, scissors or similar type of instrument in which a movable tool, for example a pivotable jaw member, is moved by manual force via a displaceable gripping member of the handle.
These known medical instruments, which are used in endoscopic surgery for instance, comprise a shaft on whose distal end a tool is disposed that comprises at least one movable jaw member and on whose proximal end a handle is disposed that is equipped with at least one movable gripping member. Said movable jaw member and said movable gripping member are connected with one another by a push/pull element for opening and closing the movable jaw member. The gripping members of the handles are geometrically configured as a rule in such a way that force exerted by the user's hand on the gripping member is markedly reinforced in transmitting to the push/pull element coupled with the jaw member, for example in a 10:1 ratio, in order to achieve sufficiently high closing power on the jaw member even without great force exertion.
To prevent such great forces from being exerted by the handle on the jaw members and/or the push/pull element, which can lead to damage or even destruction of individual components, it is taught in the art to equip medical instruments with a force-limiting apparatus, which, in the event of exceeding a borderline force, reversibly separates the components that are coupled together.
To do this, it is also familiar in the art to equip the force transmission mechanism with a predetermined breaking point. While this type of force limitation ensures secure protection of the instrument, it has the disadvantage that the instrument is not immediately ready for use again because it must be dismantled in order to repair the predetermined breaking point.
A medical instrument of this type, with a reversibly acting force-limiting apparatus, is known in the art, for example from DE 197 31 453 C2. In this known medical instrument, the force limitation is configured as an elastically reshapable part of the push/pull element that is reversibly reshaped upon exceeding the borderline force.
Also known in the art, from EP 2 269 522 A1, is a generic medical instrument whose force-limiting apparatus is configured in such a way that the force-limiting apparatus, when activated, reduces the force applied by the handle essentially to zero. This known instrument has proved itself thoroughly in practice, but it is advantageous for individual application cases to keep the force exerted by the handle even after exceeding the borderline force.